The __fastcall calling convention specifies that arguments to functions be passed in registers, when possible.

The classes in System.Runtime.CompilerServices are for compiler writers' use only.

Compilers emit custom modifiers within metadata to change the way that the just-in-time (JIT) compiler handles values when the default behavior is not appropriate. When the JIT compiler encounters a custom modifier, it handles the value in the way that the modifier specifies. Compilers can apply custom modifiers to methods, parameters, and return values. The JIT compiler must respond to required modifiers but can ignore optional modifiers. A C++ compiler could emit a custom modifier to describe how a byte should be treated in cases where the JIT compiler treats bytes in manner that is not compatible with C++ by default.

You can emit custom modifiers into metadata using one of the following techniques:

• Using methods in the System.Reflection.Emit.TypeBuilder class like erload:System.Reflection.Emit.TypeBuilder.DefineMethod, erload:System.Reflection.Emit.TypeBuilder.DefineField, erload:System.Reflection.Emit.TypeBuilder.DefineConstructor, and erload:System.Reflection.Emit.TypeBuilder.DefineProperty.

• Generating a Microsoft intermediate language (MSIL) instruction file that contains calls to modopt and modreq, and assembling the file with the MSIL Assembler (Ilasm.exe).

• Using the unmanaged reflection API.

Namespace: System.Runtime.CompilerServices
Assembly: mscorlib (in mscorlib.dll)
Assembly Versions: 1.0.5000.0, 2.0.0.0, 4.0.0.0